The invention disclosed herein relates to the intake of water from a body of water containing fish under circumstances where it is desired to hold injury to fish unavoidably drawn in with the water to a minimum. For example, in steam electric generating stations water from the body of water is utilized as cooling water which is circulated through condensors to cool and condense the steam discharged from the turbine. This cooling is essential to the efficiency of the thermo-cycle. In generating stations located along ocean coast lines or lakes and rivers it is common to pump cooling water directly from the adjacent body of water, pass it through the cooling system one time and then discharge the water. These systems are known as "once through cooling systems."
Such systems normally obtain water from the adjacent body of water by running pipes out into the body of water. Water is drawn into a bowl-like conduit structure having an upwardly facing intake orifice and then flows shoreward through the pipe to a screenwell located on the shore where trash and debris is removed. The essentially debris free water is then pumped through the condenser cooling tubes and returned to the body of water. One problem associated with these systems is that the intake structure forms an artifical reef which attracts fish. Although various improvements in the design of the intake structure have been developed to avoid drawing in fish with the intake water, some fish are still drawn into the intake pipe and are carried with the flow of water to the water-course associated with the screenwell and the folliowing pumpwell.
In the screenwell, a conventional method of screening debris and fish also in the water flowing through the water-course involves the use of vertically traveling screens arranged across the intake watercourse perpendicular to the flow of the water therein. The debris in the water impinges upon the screens and is then carried up out of the water to a collection area where it is removed from the screen. However, the fish are merely left in the screenwell and unless removed will be destroyed during the cleaning process of the screenwell area. Moreover, even if removal of the fish from the screenwell is effected such heretofore used screen systems are otherwise undesirable. Fish drawn into such systems also become impinged upon the screens. Impingement of the fish for any period of time is detrimental to the fish in that they often become weakened to disease or fall victim to predators while in their weakened condition.
Therefore it is an object of the present invention, to provide a water intake system which would satisfactorily remove trash and debris while at the same time avoid injury to the fish drawn into the intake watercourse. In providing any such new system an important consideration which must be satisfied is that the primary function of the screening system must be maintained. That is, the screenwell design must provide clean water to the circulating pumps for condenser cooling by means of an effective trash removal system which has minimum hydraulic losses. Furthermore, from an economic and system reliability standpoint, it is desirable that any new system intake design utilize as nearly as possible conventional or existing hardware.